1. Field of the Invention
The present invention is related to fuels, especially hydrocarbon fuels, and lubricants, especially lubricating oils, and, more particularly, to a class of anti-corrosion, anti-wear, anti-fatigue, and extreme pressure additives that are derived from 1,3-dithiolane-2-thiones (cyclic trithiocarbonates) for such fuels and lubricants.
2. Description of Related Art
In developing lubricating oils, there have been many attempts to provide additives that impart anti-fatigue, anti-wear, and extreme pressure properties thereto. Zinc dialkyldithiophosphates (ZDDP) have been used in formulated oils as anti-wear additives for more than 50 years. However, zinc dialkyldithiophosphates give rise to ash, which contributes to particulate matter in automotive exhaust emissions, and regulatory agencies are seeking to reduce emissions of zinc into the environment. In addition, phosphorus, also a component of ZDDP, is suspected of limiting the service life of the catalytic converters that are used on cars to reduce pollution. It is important to limit the particulate matter and pollution formed during engine use for toxicological and environmental reasons, but it is also important to maintain undiminished the anti-wear properties of the lubricating oil.
In view of the aforementioned shortcomings of the known zinc and phosphorus-containing additives, efforts have been made to provide lubricating oil additives that contain neither zinc nor phosphorus or, at least, contain them in substantially reduced amounts. Illustrative of non-zinc, i.e., ashless, non-phosphorus-containing lubricating oil additives are the reaction products of 2,5-dimercapto-1,3,4-thiadiazoles and unsaturated mono-, di-, and tri-glycerides disclosed in U.S. Pat. No. 5,512,190 and the dialkyl dithiocarbamate-derived organic ethers of U.S. Pat. No. 5,514,189.
U.S. Pat. No. 5,512,190 discloses an additive that provides anti-wear properties to a lubricating oil. The additive is the reaction product of 2,5-dimercapto-1,3,4-thiadiazole and a mixture of unsaturated mono-, di-, and triglycerides. Also disclosed is a lubricating oil additive with anti-wear properties produced by reacting a mixture of unsaturated mono-, di-, and triglycerides with diethanolamine to provide an intermediate reaction product and reacting the intermediate reaction product with 2,5-dimercapto-1,3,4-thiadiazole.
U.S. Pat. No. 5,514,189 discloses that dialkyl dithiocarbamate-derived organic ethers have been found to be effective anti-wear/antioxidant additives for lubricants and fuels.
U.S. Pat. No. 2,440,991 discloses the use of acyclic trithiocarbonates that are S,S′ di substituted with carboxylic acids of 16 to 18 carbons. These compounds are said to be useful as rust inhibitors for lubricants.
U.S. Pat. No. 2,498,936 discloses the use of acyclic trithiocarbonates as extreme pressure additives. These additives are prepared by the reaction of the salts of a trithiocarbonate with an alkyl dihalide. The use of alkyl halides in the preparation of lubricant additives is now environmentally undesirable, as this may tend to increase the levels of halogen present in the finished additive.
U.S. Pat. No. 3,166,580 discloses the preparation of dicyclopentyltrithiocarbonate from alkali metal trithiocarbonates and cyclopentyl halides, and the use of the resulting product as “lubricating additives”.
U.S. Pat. No. 3,481,871 discloses organo-sulfur derivatives that are produced by reacting a mercaptan with a sulfur chloride compound, reacting the resulting organic sulfenyl or thiosulfenyl chloride with and olefin, and finally reacting the resulting product with a metal sulfur-containing salt. The final product may be used in lubricating oils and other industrial fluids as a load-carrying additive.
U.S. Pat. No. 4,908,142 discloses additives containing a salt or complex of trithiocarbonic acid that are said to be useful in lubricants to enhance the extreme pressure/anti-wear and anti-oxidation capabilities thereof. The lubricants are preferably oils of lubricating viscosity, which may be thickened to a grease-like consistency with one or more oil thickeners, and contain from about 0.1 to about 20 weight percent of said additives.
U.S. Pat. Nos. 5,084,195 and 5,300,243 disclose N-acyl-thiourethane thioureas as anti-wear additives specified for lubricants or hydraulic fluids.
U.S. Pat. No. 6,551,966 discloses a composition comprising:
(A) a lubricant, and
(B) at least one 5-alkyl-2-mercapto-1,3,4-oxadiazole compound of the formula:
wherein R1 is a hydrocarbon or functionalized hydrocarbon of from 1 to 30 carbon atoms.
Soviet Patent Nos. SU 1,447,818; SU 1,439,098; SU 1,425,191; SU 1,361,142; SU 1,351,924; SU 1,268,573; and SU 1,082,784 describe the use of acyclic S-alkyl, S-alkyl′ disubstituted trithiocarbonates as multifunctional additives for lubricants, particularly anti-scuffing agents.
JP 46,037,176 discloses the use of the unsubstituted compound 1,3-dithiolane-2-thione as a non-corrosive extreme pressure agent for lubricants.
The disclosures of the foregoing are incorporated herein by reference in their entirety.